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Science for Medicine > How Nerves Work > Flashcards

How Nerves Work Flashcards

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Biology 101 flashcards
1
Q

Give the three subdivisions of the nervous system

A
  • the brain
  • the spinal cord
  • peripheral nerves
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2
Q

What are the two subdivisions of the peripheral nervous system?

A
  • sympathetic nervous system

- autonomic nervous system

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3
Q

Give the five components of the neurone

A
  • cell body/soma
  • dendrites
  • initial segment
  • axon
  • axon terminals
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4
Q

What part of the neurone contains the nucleus?

A

Soma

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5
Q

At what part of the neurone is the information for making action potentials arranged?

A

Initial segment

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6
Q

What part of the neurone is an important route for the information from other neurones?

A

Dendrites

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7
Q

What part of the neurone takes the action potential elsewhere?

A

Axon

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8
Q

What part of the neurone connects with other nerves/muscles and releases neurotransmitter?

A

Axon terminals

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9
Q

What is the typical RMP of neurones?

A

around -70mV

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10
Q

What pumps are present in the cell membrane?

A

Sodium/potassium pumps

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11
Q

What do potassium specific ions channels in the membranes allow?

A

Potassium to flow out down the conc gradient through facilitated diffusion

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12
Q

The electrical gradient pulling the potassium back into the cell eventually becomes equal to the conc gradient pushing the ions out of the cell. This alone would create a resting potential of -90mV, so why is RMP closer to -70mV?

A

Due to the permeability of the membrane to other ions and leaky channels

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13
Q

How do neurones communicate?

A

Using action potentials

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14
Q

What are action potentials?

A

Large all or nothing signals that can self propagate

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15
Q

What needs to happen before an AP can be fired?

A

A graded potential must reach a significant level

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16
Q

Give features of graded potentials

A
  • vary in intensity with intensity of stimulus
  • decremental
  • can only transmit over very short distances
  • can be inhibitory or excitatory depending on which ion channels are open
  • can summate through temporal or spatial summation
17
Q

What happens once a graded potential reaches the correct threshold?

A

Action potential will be fired

  • voltage gated sodium channels in the membrane open
  • sodium rushes in
  • this causes huge depolarisation of the neurone
  • this in turn causes K+ channels to open
  • cell repolarises then hyper polarises
18
Q

What effect do these graded potentials have?

A

Change the potential of the neurone to around +40mV

19
Q

Are action potentials graded or all or nothing?

A

All or nothing

20
Q

Intensity of an AP is not shown in amplitude but instead by

A

frequency

21
Q

Action potentials are

A

self-propagating, since the charge created by influx of Na+ ions spreads a bit up the axon, opening the channels there too, allowing further influx and propagation of the signal

22
Q

What three types of nerve fibre are there and what are their functions?

A

Afferent (sensory) - detect changes or sensory stimuli

Interneurones - contained within the spinal cord, decide what to do about the stimulus

Efferent (motor) - if an excitatory response is warranted, these neurones carry the signal to the effector tissues or cells

23
Q

Neurones can be ___ or ___,

and ___ or ___

A

large or small

myelinated or unmyelinated

24
Q

Large axons allow for

A

a much faster transmission speed, since resistance is decreased

25
Q

Faster transmission speed allows for

A

the charge to travel further up the axon when Na+ channels are opened, which in turn allows them to be placed further apart and less are needed

26
Q

Since the most time consuming part is the opening of these channels, reducing the number needed

A

increases transmission time

27
Q

Myelination also speeds up transmission by

A

surrounding the axon in a lipid sheath formed from Schwann cells (replaced by oligodendrocytes in the CNS)

28
Q

Sodium channels are only found

A

in the nodes of Ranvier between these sheaths which allows the transmission to travel further due to the insulation provided

29
Q

Give an example of a demyelinating disease

A

Multiple sclerosis

30
Q

Describe the consequences of demyelinating disease

A
  • eat holes in the Schwann cells
  • results in rapid decay of APs
  • preventing APs from reaching the next node and from propagating
  • conduction falls
31
Q

At the NMJ, the motor end plate from the neuronal axon comes to the muscle and

A

forms a synapse

32
Q

On the muscle side of the synapse lies the

A

sarcolemma

33
Q

The membrane of the sarcolemma has junctional folds with

A

ACh receptors, leading deeper into the muscle allowing for deeper contraction

34
Q

Describe the process of neuromuscular transmission

A
  • AP in axon opens Ca2+ channels in presynaptic terminal
  • triggers fusion of vesicles and ACh is released into the cleft
  • diffuses across and binds to receptors in the junctional folds
  • ligand gated Na+/K+ channels are opened
  • local end plate potential is produced which always reaches threshold so AP is fired, opening up voltage gated Na+ channels
  • ACh is removed by acetylcholinesterase
35
Q

Neuronal synapses are similar to the neuromuscular junctions, but the few differences make a huge amount of differences. List these differences

A
  • wide range of neurotransmitters
  • range of postsynaptic potentials
  • anatomical arrangements of synapses
  • synaptic connectivitty
36
Q

Give the four types of postsynaptic potentials

A
  • fast EPSPs
  • slow EPSPs
  • fast IPSPs
  • slow IPSPs
37
Q

Give the three anatomical arrangements of synapses

A
  • axo-somatic
  • axo-dendritic
  • axo-axonal
38
Q

Give the two types of synaptic connectivity

A
  • convergence

- divergence

Science for Medicine (24 decks)

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